A small UHF RFID tag for embedded applications in the metallic objects was proposed. Using the high dielectric ceramic as a tag antenna substrate and the folded tag antenna structure reduces the total RFID tag size compared to the conventional tag designs. The tuning slot length on ceramic top patch is used to match conjugate impedance. The proposed RFID tag antenna exhibits a reasonable radiation gain in the metal embedded environments. The maximum read range of the fabricated RFID tag in the different commercial RFID handheld reader set-up are 40 and 60 cm, respectively.

The low-profile reflectarray is proposed in this Letter based on the -negative metamaterial, whose units are mainly designed as two types for aperture phase-tuning. A tri-layer structure is investigated, which is composed of a -negative metamaterial sandwiched by two identical high- dielectric slabs, and features characteristics of high power capacity, energy tunnelling and robustness against the incident angle of the electromagnetic wave. The simulation and experiment sufficiently demonstrated that the structure obtains high transparency rate at a relative bandwidth of 30, as well as a 1-bit phase shift of 0 and 180 is achieved, which makes it potentially high-power microwave spatial phase shifter and the linear-polarisation radiator for reflectarray.

In this Letter, a quarter cylindrical dielectric resonator antenna (Q-CDRA) with a low profile and circular polarisation (CP) is presented for wideband and multiple-input–multiple-output (MIMO) systems. The approach used to obtain a reduced wideband CP antenna is realised by deforming the geometry of the CDR to a quarter cylinder and using a quasi-spiral feedline to excite two resonant modes in phase quadrature (HEM₁₁and HEM₁₂). The proposed design exhibits a wide-impedance bandwidth (BW) of 34% (4.4–6.2 GHz) with a low measured coupling level<−15 dB, and an axial ratio BW of 24.4% (4.5–5.75 GHz). The antenna gain is stable through the operating BW with a gain peak of 6.4 dBi. In addition, the antenna has a low cross-polarisation in the boresight direction with low envelope correlation coefficient<0.03. The presented design is suitable for RHCP WLAN applications.

A novel substrate integrated waveguide (SIW) cavity-backed self-diplexing leaky-wave antenna (LWA) is presented. The proposed design consists of 16 SIW cavity-backed slot elements. The SIW cavity-backed slot element can be fed by two separate ports to resonate at two different frequencies and offer good intrinsic isolation between two input ports. The proposed element is a typical self-diplexing antenna. By lining up these cavity-backed slot elements in a column, serial feeding the lower parts and the upper parts of these cavities separately, the SIW cavity-backed self-diplexing LWA can be achieved. The upper part of the proposed antenna works in 11–13.9 GHz with beam scanning from −5° to 39°. Meanwhile, the lower part works in 7.1–9.4 GHz with beam scanning from −43° to 56°. The isolation between two input ports is better than 20 dB. The measured results of the fabricated antenna prototype verify the simulation analysis.

In this study, a W-band out-of-phase active power divider, with continuously tunable power division ratio, has been presented. Out-of-phase signal is generated by the compact transform balun with accurate phase and amplitude response. To stabilise the phase difference in different power division ratio, phase-invariant cascode variable gain amplifier (VGA) is designed in the two paths of the active power divider and 4-bits proportional to absolute temperature current source is designed to control voltage of VGA. The active power divider is implemented in SiGe BiCMOS process with measured tunable power division ratio from 1:16 up to 16:1, the phase shift from 74 to 90 GHz is about 10° as the gain changes up to 12 dB, which guarantees a good phase-invariant performance.

An analysis of a frequency detection capability of the Alexander phase detector is described. Based on the analysis, a simple modified implementation achieving unilateral frequency acquisition is proposed. The probability of the output occurrence and the frequency detection gain are calculated and verified by simulation. The gain curves show that the proposed phase-frequency detector (PFD) has a unilateral frequency detection capability without a range limitation. The capability is demonstrated through transient simulation of a PLL-based clock and data recovery (CDR) utilising the proposed PFD. The CDR achieves both phase and frequency acquisitions when the initial clock frequency is lower than the data rate. Moreover, the seamless transition from frequency locking to phase locking is obtained.

This Letter presents a new combination of a broadband power amplifier (PA) and an output microstrip hairpin bandpass filter. The filter is designed based on the fifth-order Chebyshev low-pass prototype element values. Even–odd mode impedance analysis is used to calculate the filter parameters. Meanwhile, only the fundamental impedance matching is considered for this design. Therefore, a highly selective bandpass response is obtained to provide a spurious-free fundamental impedance matching. For verification, a broadband PA-filter component across 1.9–3.1 GHz (48%) is designed and fabricated. Measurements have shown a drain efficiency of 48–56.6% with 39.3–40.5 dBm of maximum output power.

A commercial graphene nanoplatelets-based tunable attenuator is proposed. The attenuator comprises of a couple of microstrip lines connected through a gap where the commercial graphene nanoplatelets are drop casted. The transmitted signal through the microstrip line can be varied by an applied DC bias voltage that alters the graphene resistance. The DC resistance of commercially acquired graphene is higher than lab-grown graphene and so is the resulting minimum attenuation of the transmitted signal. The proposed structure is designed to reduce both the minimum graphene resistance and the transmission. The resultant dynamic range of attenuation is more than twice as compared to other series attenuators designed with lab grown graphene nanoplatelets. The operating frequency of the attenuator is from 1 to 5 GHz with maximum dynamic range of attenuation almost 10 dB.

This Letter presents a non-galvanic D-band (110–170 GHz) interconnect realised in embedded wafer level ball grid array (eWLB) packaging technology. The interconnect consists of a patch-radiator-based waveguide transition implemented using one of the technology's redistribution layers. The patch radiates to a WR-6.5 standard waveguide perpendicular to its plane. An electromagnetic band-gap structure realised by metal patches is used to suppress undesired modes and improve the performance of the transition. The proposed solution is experimentally verified, and measurement results show that the transition exhibits an average insertion loss of 2 dB across the frequency range 122–146 GHz which, to the best of the authors’ knowledge, is the lowest reported loss for a D-band packaging solution in eWLB technology and hence addresses one of the main integration challenges facing millimetre-wave systems.

A coherent interference-free tunable microwave photonic notch filter with a pair of negative and positive coefficients generated by employing polarisation multiplexing and cross gain modulation in a semiconductor optical amplifier is proposed and demonstrated through simulation results. The negative and positive coefficients of the notch filter are realised through two orthogonal polarisation states of a single continuous wave laser diode. The free spectral range of microwave photonic filter is tuned by varying the differential group delay of a birefringent single-mode fibre. The proposed filter shows good tunability, easy implementation and is cost-effective.

Snowfall during cold months impacts the performance of photovoltaic (PV) installations. In real field operations, different ambient conditions often cause non-uniform snow accretion on PV panels. This can have a considerable effect on PV power production depending on array configuration, the pattern of snow coverage, and bypass diodes included in a PV system. The electrical behaviour of snow-covered PV cells is experimentally characterised. Then, the true impact of non-uniform snow accretion on PV system performance is investigated. Effect of employing bypass diodes on a PV string power generation is also verified. Different PV array layouts are studied to improve the PV harvest efficiency in cold climate regions. This research may be regarded as a practical tool for the design and selection of PV modules subjected to snowfall.

In this Letter, the authors propose a method for personnel recognition using deep convolutional neural networks (DCNNs) based on human micro-Doppler (m-D) signal separation. In which, the m-D separation algorithm is firstly performed to separate m-D signal induced by limbs movement and Doppler signal caused by torso motion, which can highlight the difference contained limbs’ m-D signatures between the same activity of different people. Afterwards, a five-layer DCNN is used to learn the necessary features directly from the separated m-D spectrogram of walking human and then implement human identification task. The method is validated on real data measured with a 5.8 GHz radar system. Experimental results show that an average recognition accuracy of about 90% can be achieved for different human group sizes.

A two-stage target detection approach, jointly performing traditional and approximate message passing (AMP) algorithms, is proposed for linear frequency-modulated continuous-wave radar. In the first stage, fast Fourier transform (FFT) and target pre-detection are carried out. Based on the pre-detection results, a reduced-dimension signal observation model is established. In the second stage, AMP is used to reconstruct true targets, and then target detection is implemented. Performances of the proposed approach are provided by numerical experiments and compared with those of AMP and the traditional FFT-based methods. Results indicate the effectiveness of the proposed approach.

The electrical responses of 55 nm silicon–oxide–nitride–oxide–silicon (SONOS) memory cells have been investigated under cryogenic conditions, and the changes of the read curves of SONOS in AC mode (programmed/erased with pulse voltage) and DC mode (programmed/erased with direct voltage sweeping) at low temperatures are compared. The experimental results show that with the decrease of temperature, the subthreshold swing of SONOS decreases, whereas the on-state current of SONOS increases. The difference in AC and DC operations causes the threshold voltage of the read curve to drift accordingly, leading to the different change in the memory window. However, in both modes of operations, the efficiencies of programming and erasing decrease at cryogenic temperatures. It is analysed that the reduction of programming efficiency at cryogenic temperatures is caused by the decrease in the quantity of pre-tunnelling electrons. The reduction in erasing efficiency is attributable to the suppression of the Poole–Frenkel effect at low temperatures, which makes it more difficult for electrons to be de-trapped.

In this Letter, a differential piezoresitive wind speed sensor on a flexible substrate is proposed. Two piezoresistors with the same size are fabricated on the front surface and back surface of the substrate, respectively. When the wind blows towards the device, the flexible substrate is bent, increasing the resistance on the front surface and reducing that on the back surface. The proposed sensor is fabricated on a polyethylene terephthalate substrate. Wind speed experiments are performed in the wind tunnel and the results demonstrate that the sensor can measure the wind speed up to about 20 m/s.

Herein, the authors characterise the dynamics of travelling pulses developed in a closed ring of oscillators with two series-connected tunnel diodes (TDs). The system exhibits multistability, i.e. several different rotation patterns coexist at a specific oscillator bias voltage. Irrespective of the rotation patterns, the oscillation amplitude is doubled by the introduction of two TDs and the phase noise is shown to be reduced significantly by self-injection locking. Moreover, the bias voltage significantly changes the pulse velocity, resulting in the voltage-controlled oscillation. These properties of rotary pulses are clarified through both time- and frequency-domain measurements of the test breadboarded circuit.

A novel floating p-well carrier stored trench bipolar transistor with L-shaped shield gates (LSG-FP-CSTBT) is proposed in this Letter. The proposed device features combinatorial L-shaped shield gates with a thick oxide layer in the lower part of the trench. Numerical analysis results show that compared to the conventional FP-CSTBT, the shield effect provided by the LSGs not only improves the trade-off relationship between the on-state voltage drop (V _CEON) and turn-off loss (E _OFF), but also improves the trade-off relationship between the turn-on loss (E _ON) of the device and reverse recovery dV _AK /dt of the antiparallel freewheeling diode. Therefore, improved device performance and reduced electromagnetic interference noise are obtained.

GaN p-n diodes were formed by selective area regrowth on freestanding GaN substrates using a dry etch, followed by post-etch surface treatment to reduce etch-induced defects, and subsequent regrowth into wells. Etched-and-regrown diodes with a 150 μm diameter achieved 840 V operation at 0.5 A/cm² reverse current leakage and a specific on-resistance of 1.2 mΩ·cm². Etched-and-regrown diodes were compared with planar, regrown diodes without etching on the same wafer. Both types of diodes exhibited similar forward and reverse electrical characteristics, which indicate that etch-induced defectivity of the junction was sufficiently mitigated so as not to be the primary cause for leakage. An area dependence for forward and reverse leakage current density was observed, suggesting that the mesa sidewall provided a leakage path.

This Letter proposes a method to reduce the effect of in-band interference in average power delay profiles obtained from frequency modulated continuous wave (FMCW) radio propagation data. The method is based on filtering the detector output in the Doppler domain. Results show that the Doppler filtering can be effective.

The application of memristor in non-linear diffusive network is introduced. A charged-controlled memristor model is used in the quantitative study of pixel-to-pixel communication via a memristor. To quantitatively understand the behaviour of the system, the authors emphasised on two cells: master and slave. Information is launched from the master cell to the slave cell through a memristor and the dynamics, as well as, the saturation of the system is observed.